Abstract

Deep levels in N-face and Ga-face -type GaNgrown by plasma-assisted molecular beam epitaxy were detected, analyzed and compared using deep level optical spectroscopy (DLOS) and conventional thermal deep level transient spectroscopy(DLTS), which together enable deep level detection throughout the GaNband gap. A redistribution of band gap states was observed between the two GaN crystal growth polarities but with a similar total trap density. Most significant was a tenfold concentration increase in a trap at that is likely related to nitrogen vacancies for the N-face polarity material, with no significant change for the Ga-vacancy-related level at . The DLOS results suggest that carbon impurities, which generate several GaNband gap states, appear to incorporate differently for both crystal polarities with the potential carbon interstitial at being undetected for N-face material. Finally, low concentrations of several new levels in the N-face -GaN not previously observed in Ga-face -GaN were observed.

Received 15 March 2010Accepted 24 May 2010Published online 18 June 2010

Acknowledgments:

The efforts at OSU and UCSB were supported by the Office of Naval Research (Grant No. N00014-09-0242) under P. Maki including support from the ONR-sponsored Millimeter Wave Initiative for Nitride Electronics (MINE) and Design-for-Reliability Initiative for Future Technologies (DRIFT) MURIs. Also, the authors acknowledge K. Nakano, G. Jessen, and R. Fitch of the Wright Patterson Air Force Base for device processing.